A tube sock that has an unopened can of Natural Ice dropped in it which can be used as a weapon. A bro sock can then be used to knock your bro out if he's about to do something stupid. It can also be used to knock some stupid ho out if she's doing something stupid.

Example 1:

Bro A: Bro, what the fuck happened last night? I think I had too many fuckin' Jagerbombs or something...

Bro D: Nah Bro, I had to hit you in the back of the head with my bro sock, you were about to fuck this nasty ho.

Bro A: Thanks, Bro.

Example 2:

Bro A: Bro, what the fuck happened to that nasty ho last night?

Bro D: Bro, I had to knock her the fuck out with my bro sock, she was trying to rape every guy at the party.